Rope pre-failure warning indicator system and method

ABSTRACT

A pre-failure indicator system for determining a degradation or failure condition includes a rope having an elongated structural strand and a pre-failure indicator strand. The pre-failure indicator strand has a tensile strength less than a tensile strength of the structural strand. The pre-failure indicator strand constructed of a conductive wire. The pre-failure indicator strand is configured to fail when the rope is subject to tension that exceeds the tensile strength of the structural strand. An indicator generates a detectable signal when the pre-failure indicator strand fails. A transceiver detects the detectable signal. The transceiver is configured to transmit a warning upon receipt of the detectable signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 61/927,744, filed on Jan. 15, 2014, entitled “Rope Pre-Failure Warning Indicator Systems,” the entire contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The preferred invention relates generally to a system for warning when a rope is about to fail and, more particularly, relates to wired-, RFID-, and fiber optic-based warning indicators that notify users or bystanders of the rope of a condition that, if not mitigated, may lead to failure of the rope or notify of imminent failure of the rope.

BACKGROUND OF THE INVENTION

Rope has many purposes, including recreational and industrial usages. Ropes come in many varieties and lengths and may be made of natural or synthetic fibers. The length, material, and strength of a given rope may be tailored to the particular applications for which the rope may be used. Heavy duty applications of rope include ship mooring and towing, industrial rigging and hoisting, and winching.

Heavy duty applications require large, often long ropes with high working load limits and high tensile strength. The working load limit of a rope relates to the maximum load capacity under which the rope should be used. The tensile strength of a rope relates to the amount of force required to break the rope. The working load limit and tensile strength are generally highest immediately after manufacture, before the rope is used.

As a rope ages as a result of exposure to environmental factors, the fibers that make up the rope may become dry, may rot or may otherwise have their strength, elasticity or other structural features degraded, thereby weakening both the working load limit and the tensile strength of the rope. In addition, as the rope is used, it may become subject to abrasion, cuts or other environmental factors to its fibers, which also weaken the working load limit and tensile strength of the rope. Other environmental factors that may weaken the working load limit and tensile strength of the rope include poor maintenance, ultraviolet radiation exposure, bending, kinks, knots, wear, fatigue, retention of water, and other related environmental factors. Individually or cumulatively, such conditions may lead to unexpected failure of the rope when the rope is in use. The likelihood of failure may be enhanced during initial acceleration and inertia, for example, at the initiation of a lifting operation.

Often, damage to rope fibers and yarns may not be detected, noticed, or raise significant concern because, for example, the length of the rope, the damage is internal, the localized damage appears to be minimal, and/or the environment where the rope is located (e.g., the rope is used under water as a mooring line). Yet, even minimal damage, in the aggregate, can set the stage for unexpected and catastrophic rope failure when the rope is exposed to excessive tension. If the damage is significant enough, on the whole, the load carrying capacity of the rope is likely less than the tensile strength of the rope before it was damaged. Rope failure may result in snap back, which can have numerous significant negative consequences for operators, users, technicians and third parties associated with the rope.

Rope snap back is a dangerous condition, and, for example, may lead to serious injury and even death to individuals located proximate the rope during a failure and snap back condition. Heavy duty uses of ropes are generally accompanied by high tension on the rope. If the rope, breaks while the rope is under high tension, each parted portion of the rope may rapidly and violently whips away from the break point. A large, heavy rope moving at snap back velocity can produce severe blunt force trauma to any individual in its path. Indeed, snap back is recognized as one of the biggest hazards to deckhands on ships. Particularly as concerns ship mooring and tugging, excessive tension applied to a rope caused by sudden changes in wind, tide, waves/wake, and water currents, coupled with an aging or damaged rope can set the stage for a hazardous condition.

There is a need in the art for ways to identify an imminent or potential rope failure or over-stress condition on a rope. An advanced warning that a rope is near its breaking point should provide operators of the rope with an opportunity to take corrective action. An advanced warning may allow individuals in the snap back zone of the rope to clear out of the way before the rope breaks. An advanced warning system will enhance safety of high tension rope operation. An advanced warning system will also provide a technician with an opportunity to repair and/or replace an over-stressed or damaged rope before failure occurs such that damage to personnel and equipment associated with the rope can be avoided.

BRIEF SUMMARY OF THE INVENTION

The disclosure features systems that indicate whether a rope is damaged, stressed, subject to excessive tension or is otherwise potentially damaged, and provides an advanced warning of a potential failure or breakage of the rope. In general, the rope systems comprise one or more ropes, including multiple rope units in which more than one of the ropes are used together to enhance the overall working load limit and tensile strength, with at least one rope comprising one or more pre-failure indicator strands that have a tensile strength that is less than the tensile strength of the rope or multiple rope unit system on the whole. Because one or more or pre-failure indicator strands have a lower tensile strength, relative to the tensile strength of the rope or rope units, one or more of these strands become compromised or otherwise break when the rope or the multiple rope unit is subject to tension that exceeds the tensile strength of the one or more pre-failure strands. The one or more pre-failure indicator strands comprise an indicator that provides information about the state of the strands, and by proxy, the state of the rope.

The rope may comprise natural materials, synthetic materials, or a hybrid of natural and synthetic materials. The fibers or strands of the rope, including structural strands and pre-failure warning indicator strands, generally comprise such materials. The one or more pre-failure indicator strands may comprise materials that are capable of being degraded by environmental factors, such as exposure to ultraviolet radiation (e.g., from the sun) at a faster rate than the natural or synthetic materials from which the structural strands or units of the rope are fabricated. The one or more pre-failure indicator strands may also comprise materials that are capable of being degraded by abrasion (e.g., by dirt or grit or by use of the rope or the rope coming into contact with various surfaces that may abrade the rope) at a faster rate than the natural or synthetic materials from which the structural strands of the rope are fabricated. The one or more pre-failure indicator strands may further comprise materials that are capable of being degraded by environmental factors, such as exposure to ultraviolet radiation or other environmental conditions (e.g., from exposure to the elements, and advanced age) at a faster rate than the natural or synthetic materials of which the structural strands of the rope are fabricated. The one or more pre-failure indicator strands may also comprise materials that are capable of being fatigued (e.g., from mechanical movement of the rope over time) at a faster rate than the natural or synthetic materials out of which the structural strands of the rope are fabricated.

The preferred indicator may generate a detectable signal. The indicator may comprise a dye that is released when one or more of the strands become compromised or otherwise break. Thus, a dye may comprise a detectable signal. The detectable signal may comprise a radio frequency signal, an electrical signal, or a light signal. The systems also may comprise a detector that detects the detectable signal and the detector may comprise a transceiver that detects the detectable signal, determines whether the one or more pre-failure indicator strands has broken based on the presence or the absence of the detectable signal, and transmits a warning or alarm if the one or more pre-failure indicator strands has broken. The warning may comprise a warning signal. The alarm may comprise an audible alarm, a visible alarm, and/or a tactile alarm upon the overstressing of the rope or breakage of the indicator strand. The transceiver may emit the alarm, or may signal an alarm generator to emit the alarm.

In some aspects, the indicator comprises a radio frequency identification (“RFID”) tag. The RFID tag may be an active RFID tag that includes a power source that allows the tag to generate a detectable signal. The RFID tag may be a passive or semi-passive RFID tag that generates a detectable signal upon coming into contact with a signal generated from an RFID detector that powers the RFID tag components in order to generate the detectable signal. The detector and/or transceiver may thus comprise an RFID signal detector. In aspects in which an active RFID tag is used, the one or more pre-failure indicator strands preferably comprise a shield that blocks the detectable signal generated from the active RFID tag. Thus, although the RFID signal is substantially continuously generated, the signal is not detected when it is blocked by the shield. The absence of the RFID signal indicates that the one or more pre-failure indicator strands have maintained their integrity. But when the one or more pre-failure indicator strands become compromised or break, the shield also breaks such that the RFID signal is no longer blocked, and may be freely detected. The presence of an unshielded, detectable RFID signal indicates that the one or more pre-failure indicator strands have lost their integrity.

In some aspects, the one or more pre-failure indicator strands comprises a conductive wire and the indicator comprises an electrical signal generator. The electrical signal may comprise an electrical current, an analog signal, a digital signal, any combination of an electrical current, an analog signal or a digital signal and nearly any variety of signal that may be transmitted and detected upon over-stress or breakage of strands and/or fibers of the rope. The detector and/or transceiver may thus comprise an electrical signal detector. The electrical signal is preferably generated by the electrical signal generator, traverses the conductive wire, and is detected by the electrical signal detector. The presence of the electrical signal indicates that the one or more pre-failure indicator strands have maintained their integrity, however, when the one or more pre-failure indicator strands become compromised or break, the electrical signal can no longer traverse the conductive wire and can no longer be detected. The absence of the electrical signal indicates that the one or more pre-failure indicator strands have lost their integrity.

In some aspects, the one or more pre-failure indicator strands comprise one or more fiber optic cables and the indicator comprises a light source. The one or more fiber optic cables may comprise a simplex or a duplex arrangement. The detector and/or transceiver may thus comprise a light detector. The light is generated by the light source, traverses the one or more fiber optic cables, and is detected by the light detector. The presence of the light signal indicates that the one or more pre-failure indicator strands have maintained their integrity, but when the one or more pre-failure indicator strands become compromised or break, the light signal can no longer traverse the one or more fiber optic cables and can no longer be detected. The absence of the light signal indicates that the one or more pre-failure indicator strands have lost their integrity. In addition, if the fiber optic cable becomes partially damaged or compromised at a particular location, the light signal changes, the light detector may detect the change in the light signal and provide an indication that the fiber optic cable is damaged or partially damaged.

In some aspects, the one or more pre-failure indicator strands comprises one or more tubes or a plurality of pouches and the indicator comprises a dye. The dye may comprise a colored dye and may comprise an ultraviolet dye. The dye is enclosed within the one or more tubes or the pouches. Upon release from the enclosure, the dye permeates the rope fibers and reaches the external surface of the rope, where it can be detected. The absence of the dye on the rope surface indicates that the one or more pre-failure indicator strands have maintained their integrity, but when the one or more pre-failure indicator strands become compromised or break, the dye may be detected. The presence of the dye on the rope surface indicates that the one or more pre-failure indicator strands have lost their integrity.

The invention also features methods for detecting whether a rope is damaged, stressed, or subject to excessive tension. In general, the methods comprise determining whether one or more pre-failure indicator strands of a rope have broken by detecting the presence or the absence of a detectable signal generated by an indicator operably connected to the one or more pre-failure indicator strands. The methods may further comprise taking remedial action to avoid failure of the rope. The methods may further comprise producing an audible alarm, a visible alarm, and/or a tactile alarm if it is determined that one or more pre-failure indicator strands of the rope have broken.

The methods may be used in accordance with any of the ropes, multiple rope units, or pre-failure indicator systems described or exemplified herein. For example, the method steps may be carried out through the structural components of the ropes and the systems. These structural components include any of the structures described or exemplified herein. In accordance with the methods, the detectable signal may comprise the release of an indicator dye, or may comprise an electrical signal, or may comprise a light signal.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIG. 1 is a front elevational view of a rope pre-failure indicator system in accordance with a first preferred embodiment of the present invention, wherein a portion of a rope is shown with cross-sections taken along a longitudinal plane of the rope and at one end at a plane substantially perpendicular to the longitudinal axis of the rope;

FIG. 2A is front elevational view of the rope pre-failure indicator system of FIG. 1 with a different arrangement of RFID tags and wherein cross-sections are taken along a longitudinal plane of the rope and at one end at a plane substantially perpendicular to the longitudinal axis of the rope;

FIG. 2B is a front elevational view of a rope pre-failure indicator system in accordance with a second preferred embodiment of the present invention, wherein a portion of a rope is shown with cross-sections taken along a longitudinal plane of the rope and at one end at a plane substantially perpendicular to the longitudinal axis of the rope;

FIG. 2C is a front elevational view of a rope pre-failure indicator system in accordance with a third preferred embodiment of the present invention, wherein a portion of a rope is shown with cross-sections taken along a longitudinal plane of the rope and at one end at a plane substantially perpendicular to the longitudinal axis of the rope;

FIG. 2D is a front elevational view of a rope pre-failure indicator system in accordance with a fourth preferred embodiment of the present invention, wherein a portion of a rope is shown with cross-sections taken along a longitudinal plane of the rope and at one end at a plane substantially perpendicular to the longitudinal axis of the rope;

FIG. 3 is a front elevational view of a portion of a multiple-rope unit in accordance with a fifth preferred embodiment of the present application, including RFID tags in accordance with the first preferred embodiment of the present invention;

FIG. 4 is a front elevational view of the portion of the multiple-rope unit of FIG. 3, including RFID tags in accordance with the first preferred embodiment of the present invention;

FIG. 5 is a front elevational view of the portion of the multiple-rope unit of FIG. 3, including a fiber optic cable in accordance with the second preferred embodiment of the present invention;

FIG. 6 is a front elevational view of the portion of the multiple-rope unit of FIG. 3, including a conducting wire in accordance with the third preferred embodiment of the present invention; and

FIG. 7 is a front elevational view of the portion of the multiple-rope unit of FIG. 3, including indicator dye in accordance with the fourth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Various terms relating to aspects of the disclosure are used throughout the specification and claims. Such terms are to be given their ordinary meaning in the art, unless otherwise indicated. Other specifically defined terms are to be construed in a manner consistent with the definition provided herein.

Certain terminology is used in the following description for convenience only and is not limiting. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. The words “right,” “left,” “lower,” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center or orientation of the device and related parts thereof. The terminology includes the above-listed words, derivatives thereof and words of similar import.

The disclosure relates to systems and methods for determining whether rope failure is imminent, for example, because the rope is overloaded or is under excessive tension. Foundational features include radio frequency identification tags, fiber optics, conductive wires, and sensors that convey information about the condition of the rope to a user.

Referring to FIG. 1, a rope pre-failure indicator system 10 a for a single rope in accordance with a first preferred embodiment of the present invention is illustrated. The first preferred pre-failure indicator system 10 a includes a rope 20 having structural strands 22 of nearly any type. The rope 20 may be comprised of a plurality of structural strands 22 that may be constructed of any suitable number of yarns and fibers fabricated from any suitable natural or synthetic material or a combination of natural and synthetic materials. The rope 20 is not limited to including the plurality of structural strands 22 and may include a single elongated structural strand 22 that is designed and configured to carry a tensile load of a predetermined capacity. The structural strand 22 has a longitudinal axis that extends through the strand 22 from a first end to a second end. The longitudinal axis of the structural strand 22 generally follows a centerline of the structural strand 22 and/or rope 20 and may bend or arc if the strand 22 and/or rope 20 is positioned in a bent or arced position, such as the positions and/or orientations of the strands 22 in FIGS. 3-7. The rope 20 and structural strands 22 may have any working load limit and any tensile strength. In preferred configurations, the strands 22 may have a working load limit in the approximate range of one thousand (1,000) to one million pounds (1,000,000) and a tensile strength in the approximate range of five thousand (5,000) to five million (5,000,000) pounds, but are not so limited. The strands 22 may have nearly any working load limit and/or tensile desired by the designer and/or user, for example, the strands 22 may have a maximum breaking load greater than five million (5,000,000) pounds for certain offshore mooring applications. The system 10 a and methods are useful, among other things, for mooring, lifting, winching, and hoisting applications, or any other applications in which snap back is a concern. Each of the systems 10 a, 10 b, 10 c, 10 d, 10 f of the preferred embodiments are also useful, among other things, for mooring, lifting, winching, and hoisting applications, or any other applications in which snap back or nearly any variety of failure of the rope 20 is a concern.

The rope 20 may be comprised of natural fibers (e.g., hemp, jute, or other suitable natural material) or synthetic fibers (e.g., polyester, polyethylene, nylon, K-Spec® (Slingmax, Inc.), high-modulus polyethylene (“HMPE”), liquid crystal polymer (“LCP”), aramid, para-aramid, or other suitable synthetic material) or a combination of any suitable proportion of natural fibers and synthetic fibers. The rope 20 may be comprised of any suitable number of such structural strands 22. The fibers of the structural strands 22 may be comprised in a yarn. A plurality of yarns may be assembled to comprise a strand 22. A plurality of strands 22 may be assembled to comprise the rope 20. The rope 20 may comprise any structure (e.g., laid, wound, braided, plaited). The rope 20 may comprise a core of a plurality of structural strands 22 and an outer sheath comprising a plurality of structural strands 22. The rope 20 may have any length.

The rope preferably includes one or more pre-failure indicator strands 30. The one or more pre-failure indicator strands 30 preferably are integral of interwoven with the structural strands 22 that together comprise the rope 20, but in some aspects, the one or more pre-failure indicator strands 30 are external to the main body of the rope 20 or a bundle of structural strands 22. In some aspects, the one or more pre-failure indicator strands 30 comprise a core of the rope 20 around which the plurality of structural strands 22 are wrapped. The one or more pre-failure indicator strands 30 may comprise a plurality of interwoven fibers that together constitute a yarn, with a plurality of yarns interwoven together to constitute the strand 30. The one or more pre-failure indicator strands 30 need not be the same size or have the same make-up as the structural strands 22 that make up the rope 20, such that the one or more pre-failure indicator strands 30 may be a substructure of the rope 20, or may be made of a different material, or a different number of fibers, or a different number of yarns, or have different properties relative to the structural strands 22 that make up the rope 20. In some aspects, the one or more pre-failure indicator strands 30 may be substantially identical to the structural strands 22, except the one or more pre-failure indicator strands 30 may be pre-damaged in order that they may fail at a tension that is less than the tensile strength rating of the rope 20. For example, in a preferred configuration, the structural strands 22 may be designed and configured to fail at a load of approximately two hundred thousand pounds (200,000 lbs) and the indicator strand 30 may be designed and configured to fail at a load of one hundred sixty thousand pounds (160,000 lbs) or approximately eighty percent (80%) of the failure load of the structural strands 22. The structural strands 22 and indicator strand 30 are not limited to such a ratio or to such failure loads, but the described ratio and failure loads comprise a non-limiting preferred configuration that a designer or user may desire.

In some aspects, the one or more pre-failure indicator strands 30 comprise a material that degrades under exposure to environmental factors, such as ultraviolet light/radiation at a rate that is faster than the structural strands 22 of the rope 20 degrade under ultraviolet light/radiation. In some aspects, the one or more pre-failure indicator strands 30 comprise a material that degrades under abrasive forces at a rate that is faster than the structural strands 22 degrade under abrasive forces. In some aspects, the one or more pre-failure indicator strands 30 comprise a material that dries or dry rots at a rate that is faster than the structural strands 22 dry or dry rot. In other preferred aspects, the one or more pre-failure indicator strands 30 comprise a material that fatigues at a rate that is faster than the structural strands 22 fatigue.

The one or more pre-failure indicator strands 30 may be positioned at any suitable location among the structural strands 22, including substantially near the center of the rope 20, substantially near the edge of the rope 20 or at any other position between the center and edge of the rope 20. The one or more pre-failure indicator strands 30 may also be located at a position to best identify interior fatigue or damage to the rope 20. The one or more pre-failure indicator strands 30 may span substantially the entire length of the rope 20 or may be positioning in the rope 20 at predetermined lengths or portions, for example, where failure of the rope 20 is expected or frequent or where the rope 20 is typically fatigues, degraded, damaged, abraded or otherwise has a tendency or history of failure. In addition, the pre-failure indicator strands 30 may be positioned at locations on the rope 20 where visual inspection is difficult or impossible and the pre-failure indicator strands 30 may be monitored via non-visual mechanisms and methods, as described herein.

In the preferred embodiments, the one or more pre-failure indicator strands 30 have a tensile strength that is less than the tensile strength of the structural strands 22, such that the one or more pre-failure indicator strands 30 breaks at a rope tension that is less than the tension under which the rope 20 itself will break. The tensile strength of the one or more pre-failure indicator strands 30 may be at or slightly above the working load limit of the structural strands 22 and substantially below the tensile strength of the structural strands 22. The tensile strength of the one or more pre-failure indicator strands 30 preferably lies between the working load limit and the tensile strength of the structural strands 22 on the whole, such that the one or more pre-failure indicator strands 30 will break before the rope 20 itself breaks. For example, in a preferred configuration, the rope 20 may comprise a three-strand rope 20 having a maximum load of two hundred thousand pounds (200,000 lbs), wherein the two structural strands 22 have a tensile strength of seventy-one thousand pounds (71,000 lbs) and the single indicator strand 30 has a tensile strength of fifty-eight thousand pounds (58,000 lbs), wherein the rope 20 may be constructed of a high-modulus polyethylene (“HMPE”) material. The one or more pre-failure indicator strands 30 may indicate upon failure or damage that the rope 20 is stressed such that corrective action or clearance of the snap back zone or other zone in the vicinity of the rope 20 may be undertaken in advance of failure of the rope 20. In addition, failure or damage to the pre-failure indicator strands 30 may indicate that replacement or repair of the rope 20 is necessary or that inspection of the rope 20 is necessary before additional significant loads are applied to the rope 20.

The one or more pre-failure indicator strands 30 are preferably operably connected to an indicator that generates a detectable signal or is otherwise capable of generating a detectable signal. The one or more pre-failure indicator strands 30 may comprise a conduit for this detectable signal such that the detectable signal may traverse the one or more pre-failure indicator strands 30.

In the first preferred embodiment, as shown in FIG. 1, the one or more pre-failure indicator strands 30 includes a plurality of RFID tags 40 attached thereto or integrated therein. Each RFID tag 40 is capable of generating a detectable signal, for example, an RFID signal such as a radio wave. The first preferred embodiment is not limited to including RFID tags 40, as the RFID tags 40 may be comprised of nearly any type or variety of wireless radio technology that transmits or is configured to transmit a signal when desired by the designer. The one or more pre-failure indicator strands 30 may include a plurality of passive RFID tags 40 attached to the pre-failure indicator strands 30. The passive RFID tag 40 typically does not include its own power source, but may include components that generate a current to power the RFID tag 40 when such components are brought into proximity of emissions from an RFID transceiver 42. The one or more pre-failure indicator strands 30 may include a plurality of semi-passive RFID tags 40, which preferably include their own power source, but the power source does not drive signal transmission from the RFID tag 40. The one or more pre-failure indicator strands 30 may include a plurality of active RFID tags 40. An active RFID tag 40 includes a power source, preferably a battery, to power the RFID tag 40 and transmit the signal. The active RFID tag 40 preferably transmits a continuous signal. As shown in FIG. 2A, the one or more pre-failure indicator strands 30 may include one or more elongate RFID tags 40, which extend over significant lengths of the pre-failure indicator strands 30.

The one or more pre-failure indicator strands 30 may include a shield 44 that blocks the RFID tag 40 signal, such that the signal may only be detected when the shield 44 is compromised, thereby indicating that the one or more pre-failure indicator strands 30 are also compromised, with a compromised pre-failure indicator strand 30 indicating that the rope 20 is stressed, including that the rope 20 is under excessive tension, including tension that exceeds the tensile strength of the one or more pre-failure indicator strands 30 or that failure of the rope is approaching or is imminent. The shield 44 may comprise aluminum, shielding polymeric materials or other suitable materials that are known in the art as capable of blocking an RFID signal. When the shield 44 is compromised and at least one of the RFID tags 40 is not compromised, the RFID signal is no longer blocked such that the RFID tag 40 may still transmit the signal, which may freely pass through the compromised shield 44 and thereafter be detected by the RFID signal transceiver 42. Compromised, as used herein, includes, but is not limited to cracking, breaking, rupturing, fragmenting, damaging, severing, and other forms of damage. The rope pre-failure indicator system 10 a of the first preferred embodiment also includes an RFID signal transceiver 42.

The RFID signal transceiver 42 may transmit a signal that activates a passive RFID tag 40 in order that the passive RFID tag 40 may transmit its signal. The RFID signal transceiver 42 may receive the signal from a passive or active RFID tag 40. In some aspects, when the RFID signal, formerly blocked by the shield 44, is freed by a compromised shield 44, the RFID signal transceiver 42 receives the signal from the RFID tag 40. Receipt of the RFID signal indicates that the one or more pre-failure indicator strands 30 at least is compromised and may have broken. The RFID signal transceiver 42 may then warn a user and/or individuals in the vicinity of the rope 20 or its snap back zone, through an audible alarm, a visible warning, and/or a tactile alarm such as vibration. The RFID signal transceiver 42 may itself issue the warning or alarm or may cause a separate device to issue the warning or alarm or the recipient of a warning message from the RFID signal transceiver 42 may issue the warning or alarm. Having received the warning signal, alarm or warning message, the user may take corrective action and/or any individual in a danger area may extricate themselves from the area.

Referring to FIG. 2B, in an alternative or second preferred embodiment of a rope pre-failure indicator system 10 b, the one or more pre-failure indicator strands 30 may be comprised of, in addition to or in lieu of RFID tags 40, one or more fiber optic cables 50 (FIG. 2B). The one or more pre-failure indicator strands 30 may be one or more fiber optic cables 50. The one or more fiber optic cables 50 transmit light between a first terminal 54 a, which is preferably positioned at a first end of the rope 20, and a second terminal 54 b, which is preferably positioned at a second end of the rope 20. The first and second terminals 54 a, 54 b are operably connected to the ends of each fiber optic cable 50 that may be included in the rope 20. The first and second terminals 54 a, 54 b are not limited to being connected to or positioned at the ends of the rope 20 and may be positioned at any location between ends of the rope 20, for example, at opposite sides of a location on the rope 20 wherein failure, damage and/or fatigue are expected to occur or likely to occur on the rope 20. In addition, the first and second terminals 54 a, 54 b may be positioned at opposite sides of a portion of the rope 20 that is located where visual inspection of the rope 20 is difficult or impossible to monitor the integrity of the rope 20 in such locations.

A detectable signal transmitted through the fiber optic cable 50 may comprise light. The terminals 54 a, 54 b may transmit and/or receive a light signal, which passes through the fiber optic cable 50. Each terminal 54 a, 54 b may comprise a transmitter on one end of each fiber optic cable 50 and a receiver on the other end of each fiber optic cable 50. Thus, each terminal 54 a, 54 b may comprise a fiber optic transmitter, a fiber optic receiver, or a fiber optic transceiver. In some aspects, at least one fiber optic cable 50 transmits light in one direction and at least one fiber optic cable 50 transmits light in a reverse direction, for example, as part of a duplex transmission. In some aspects, one or more fiber optic cables 50 alternate the direction of the light transmission in the same cable 50.

Each terminal 54 a, 54 b may include a signal generation source 56 a, 56 b, preferably a light source 56 a, 56 b that is operably connected to each fiber optic cable 50. The light source 56 a, 56 b may be any suitable light source 56 a, 56 b, including a light emitting diode or a laser such as a fabry-perot (“FP”) laser, distributed feedback (“DFB”) laser or a vertical cavity surface-emitting laser (“VCSEL”) that is operably connected to each fiber optic cable 50. The signal generation source 56 a, 56 b may also be comprised of an electric generation source, a vibration generation source or nearly any other source that is configurable to send a signal into the cable 50. Each terminal 54 a, 54 b may also include a detector 58 a, 58 b, which is operably connected to each fiber optic cable 50, detects the light and converts the light into a signal that is transmitted to a receiver 52.

Under non-stressed or non-load conditions, the integrity of the one or more fiber optic cables 50 is maintained such that the light emitted by the light source 56 may freely traverse the fiber optic cable 50 between each terminal 54 a, 54 b. In the non-load condition, the transmitted light may be detected by the detector 58. In overloaded conditions, the one or more pre-failure indicator strands 30 may be compromised or break, for example, because the tension on the rope 20 exceeds the tensile strength of the one or more pre-failure indicator strands 30 or the elongation of the rope 20 exceeds the maximum elongation of the pre-failure indicator strands 30. The one or more fiber optic cables 50 are compromised such that the integrity of the one or more fiber optic cables 50 is not maintained or the fiber optic cables 50 break in the overload condition and the light only partially traverses or does not traverse the fiber optic cable 50 between each terminal 54 a, 54 b and cannot be detected by the detector 58. Interruption of the light transmission between each terminal 54 a, 54 b indicates that the rope 20 is stressed, is under excessive tension or that failure of the rope 20 is approaching or imminent. As a non-limiting example, the fiber optic cable 50 may have a maximum elongation of approximately four percent (4%) and the structural strands may have a maximum elongation of approximately five percent (5%), such that the fiber optic cable 50 breaks before the structural strands 22 break during use. The fiber optic cable 50 may be constructed of glass, plastic, polymeric materials or nearly any material that is able to take on the size and shape of the fiber optic cable 50, perform the described functions of the fiber optic cable 50 and withstand the normal operating conditions of the rope 20 and fiber optic cable 50.

The receiver 52 may comprise a processor, and may comprise a computer or a handheld device. The receiver 52 indicates to a user that a failure or reduction in light transmission has been detected, meaning that the rope 20 has been subject to high or excess tension and that if the situation is not mitigated or remedied, the rope 20 may fail. In addition, if the overload situation cannot be mitigated or remedied in sufficient time, failure of the rope 20 is possible or imminent. The receiver 52 may, for example, warn a user or individuals in the vicinity of the rope 20, including a snap back zone or other danger zone, through an audible alarm, a visible warning, and/or a tactile alarm such as vibration that a potential failure or overload condition is detected and the rope 20 may require repair or the snap back zone may require evacuation for unloading of the rope 20. Having received the warning signal from the receiver 52, the user may take corrective action and/or bystanders may move to a safe location away from the snap back or danger zone of the rope 20. In addition, the receiver 52 may be able to detect reduced transmission of light through the fiber optic cable 50 and may be able to detect a distance from the first and/or second terminal 54 a, 54 b where the reduction in light occurs. Such detection may permit the operator to determine where damage occurred to the fiber optic cable 50 and an estimate of the damage such that the rope 20 can be repaired, reinforced, replaced or otherwise corrected to ensure proper operation of the system associated with the rope 20. In addition, this technique may be able to detect location of abrasion, fatigue and/or environmental breakdown of the rope 20, which the operator or a technician can remedy prior to the occurrence of any catastrophic failure of the rope 20.

Referring to FIG. 2C, in an alternative or third preferred embodiment of a rope pre-failure indicator system 10 c, the one or more pre-failure indicator strands 30 may comprise, in addition to or in lieu of RFID tags 40 and in addition to or in lieu of one or more fiber optic cables 50, one or more conductive wires 60. The one or more pre-failure indicator strands 30 may be comprised of one or more of the conductive wires 60. The one or more conductive wires 60 transmit electrical signals between first and second terminals 64 a, 64 b, preferably connected to opposite ends of the rope 20 and operably connected to each end of each conductive wire 60. The first and second terminals 64 a, 64 b are not limited to being connected to opposite ends of the rope 20 and may be connected at locations between the ends of the rope 20. The terminals 64 a, 64 b may transmit and/or receive an electronic signal, which passes through the conductive wire 60. Thus, a detectable signal may comprise an electronic signal. Each terminal 64 a, 64 b may comprise a transmitter on one end of conductive wire 60 and a receiver on the other end of the conductive wire 60. Thus, each terminal 64 a, 64 b may comprise an electronic signal transmitter, an electronic signal receiver, or an electronic signal transceiver. In its simplest form, the electronic signal may comprise an electric current. The signal may comprise an analog or digital signal. The one or more conductive wires 60 is preferably constructed of a metal that is capable of conducting electricity or electrical signals, including copper or silver, or other suitable conductive metal. The conductive wires 60 may alternatively be constructed of other conductive materials, such as carbon fibers, conductive polymeric materials or other materials that are designed and configured to conduct signals, such as an electrical current, between the first and second terminals 64 a, 64 b. The conductive wire 60 may alternatively or, in addition, be constructed of a material designed and configured to degrade at a faster rate than the structural strands 22 based on exposure an environmental factor. The environmental factor may include ultraviolet radiation, abrasion, dry rot or other related environmental factors that may impact the strength, elasticity, toughness or other structural features of the structural strands 22 during normal operating conditions and, generally, over a period of time in the operating conditions.

Each terminal 64 a, 64 b may comprise a signal source 66 a, 66 b, which may comprise a current source and/or a voltage source. The signal source 66 a, 66 b may comprise a processor. The signal source 66 a, 66 b may comprise a signal generator, including an analog signal generator, a function generator, a microwave signal generator, a pitch generator, an arbitrary waveform generator, a frequency generator, or other suitable signal generator known in the art. The signal source 66 a, 66 b is operably connected to each end of the conductive wire 60. Each terminal 64 a, 64 b may also include a detector 68 a, 68 b, which is operably connected to each conductive wire 60, detects the electronic signal and converts it into a warning or conveys the signal to an electronic signal receiver 62.

Under non-stressed conditions, the integrity of the one or more conductive wires 60 is maintained such that the electrical signal generated by the signal source 66 a, 66 b may freely traverse the conductive wires 60 between each terminal 64 a, 64 b and may be detected by the electronic signal receiver 62. When the one or more pre-failure indicator strands 30 are compromised, for example, because the tension on the rope exceeds the tensile strength of the one or more pre-failure indicator strands 30, the one or more conductive wires 60 may become compromised such that the integrity of the one or more conductive wires 60 is not maintained and fails. As a non-limiting preferred example, the conductive wire 60 may be comprised of an eighteen (18) gauge copper wire 60 that is preferably sized such that it is not destroyed by crushing forces of the structural strands 22 during use. The conductive wire 60 could be inserted into a rope 20 having a working load limit of two hundred thousand pounds (200,000 lbs) for providing a pre-warning indication of potential damage to the rope 20 or degradation of the properties of the rope 20. When the conductive wire 60 fails, the electrical signal does not traverse the conductive wires 60 between the first and second terminals 64 a, 64 b or may travel through the conductive wire 60 at a lower volume, level or rate. The change in flow of signal through the conducting wire 60 is communicated from the first and/or second terminals 64 a, 64 b to the receiver 62. Interruption and/or change of the electrical signal transmission between the terminals 64 a, 64 b may indicate that the rope 20 is stressed or damaged, including that the rope 20 is under excessive tension or that failure of the rope 20 is likely or imminent. For example, interruption of the electrical signal transmission between the terminals 64 a, 64 b may indicate that the load has exceeded the recommended working load limits of the structural strands 22 and has exceeded the tensile strength of the indicator strand 30, thereby indicating that the rope 20 has been subjected to a load exceeding its recommended working load, capacity or rated load. The receiver 62 preferably provides a warning signal to the user as a result of the change in the flow of signal through the conducting wire 60, such as a visual or audible signal to the user. The receiver 62 may also send a warning or maintenance message to predetermined individuals via nearly any form of messaging, such as telephone, text, email or other related messaging means and mechanisms.

Referring to FIG. 2D, in an alternative or fourth preferred embodiment of a rope pre-failure indicator system 10 d, the one or more pre-failure indicator strands 30 may comprise, in addition to or in lieu of RFID tags 40, fiber optic cables 50, or conductive wires 60, a visual overload indicator such as an indicator dye 70. The one or more pre-failure indicator strands 30 may include one or more tubes or one or more pouches that contain the indicator dye 70. The tubes or pouches are preferably frangible, and thus are compromised when the rope 20 is subject to tension that exceeds the tensile strength of the one or more pre-failure indicator strands 30, thereby releasing the indicator dye 70. The tubes or pouches may comprise any suitable material, including a plastic, polymeric, composite, glass, or other material that may flex yet break at desired tension levels. Once released, the indicator dye 70 preferably diffuses or flows through the structural strands 22 or flows onto an external surface of the rope 20 where the indicator dye 70 can be visually detected and inspected by a user. The indicator dye 70 may be any suitable dye that can be detected, and may comprise a color, and/or may comprise a fluorescent color, and/or may comprise an ultraviolet dye that may be detected via ultraviolet light. In addition, the visual overload indicator 70 may be comprised of nearly any material that provides a visual indication on the surface of the rope 20 to provide a visual indication or warning to the user that the rope 20 has been damaged or subjected to an overload condition.

Under non-stressed conditions, the integrity of the one or more pre-failure indicator strands 30 and the visual overload indicator 70 is maintained such that the tube or pouch retains the preferred dye 70. When the one or more pre-failure indicator strands 30 are compromised, for example, because the tension on the rope 20 exceeds the tensile strength of the one or more pre-failure indicator strands 30, the tubes or pouches are compromised such that the indicator dye 70 is released from its enclosure and can be detected. Release of the indicator dye 70 may also occur when the rope 20 is not under tension or being used and in such cases may signal internal damage to the rope 20, including abrasive or dry rot damage that has occurred in at least some locations throughout the rope 20 or damage to portions of the structural strands 22. In such cases, the rope 20 may be removed from service or used at lower working load limits or at lower tension to avoid failure.

Detection of the presence of the indicator dye 70 on the rope 20 surface indicates that the rope 20 is stressed, including that the rope 20 is under excessive tension or that failure of the rope 20 is imminent or may occur if the load is not removed from the rope 20. Detection may be according to any suitable methodology, including visual inspection, or by use of a light source 72 which may aid visual inspection where there is insufficient ambient light or by use of an ultraviolet light source 72, which would allow visualization of the presence of the ultraviolet dye 70. In some aspects, a detector 74 for detecting the indicator dye 70 may be used.

Detection of an indicator dye 70 may be automated, for example, with the use of equipment 76 that continually monitors the rope 20 for the presence of the indicator dye 70 on the surface of the rope 20. The monitoring equipment 76 may include a processor and an alarm generator 78 that emits an audible alarm, a visible alarm, and/or a tactile alarm upon the detection of the indicator dye 70, thereby warning a user or individuals in the vicinity of the rope 20, including a snap back zone or other danger zone of a pre-failure condition in the rope 20. Having received an alarm from the monitoring equipment 76, the user may take corrective action, and/or bystanders may move to a safe location away from the snap back or danger zone of the rope 20.

For manual monitoring, for example, by visual detection, including through the use of a light source 72, the individual carrying out inspection of the rope 20 may utilize an alarm generator 78, which the user may activate to emit an audible alarm, a visible alarm, and/or a tactile alarm, when a pre-failure condition in the rope 20 is detected.

Ropes 20 having the features described herein are also provided in accordance with the disclosure. For example, in some aspects, the rope 20 may include one or more pre-failure indicator strands 30 having a tensile strength greater than the working load limit of the rope 20 and less than the tensile strength of the rope 20 or the structural strands 22, such that the one or more pre-failure indicator strands 30 break when the rope 20 is subject to tension that exceeds the tensile strength of the one or more pre-failure strands 30. In some preferred aspects, the one or more pre-failure indicator strands 30 comprise a plurality of active RFID tags 40, which may comprise a shield 44 that blocks transmission of the RFID signal generated by the RFID tags 40 until the shield 44 is compromised. In some preferred aspects, the one or more pre-failure indicator strands 30 comprise a conductive wire 60. In some preferred aspects, the one or more pre-failure indicator strands 30 comprise one or more fiber optic cables 50. In some preferred aspects, the one or more pre-failure indicator strands 30 comprise one or more tubes or one or more pouches that contain an indicator dye 70. The ropes 20 may include other features described or exemplified herein, including an indicator that generates a detectable signal such as a light source 56, 72, an electrical signal generator 66, a light detector 58, 72 or an electrical signal detector 68.

Referring to FIGS. 3-7, in an alternative or fifth preferred embodiment of a rope pre-failure indicator system 10 f, the rope pre-failure indicator system 10 f may be used in a multiple rope unit. For example, in some applications, multiple ropes 20 a, 20 b, 20 c are used together to enhance the overall working load limit and tensile strength of a system. Two or more ropes 20 a, 20 b, 20 c, each including at least one structural strand 22, may be combined into a multiple rope unit, for example, three ropes 20 a, 20 b, 20 c may be combined into a multiple rope unit, but the system 10 f is not so limited and the system may include more or less than three ropes 20 a, 20 b, 20 c. In some aspects, four, five, six, seven, eight, nine, ten, eleven, twelve, or more than twelve ropes 20 a, 20 b, 20 c may be combined into a multiple rope unit. Each rope 20 a, 20 b, 20 c in the multiple rope unit does not need to be physically joined to an adjacent rope 20 a, 20 b, 20 c and it is sufficient that a plurality of ropes 20 a, 20 b, 20 c are in proximity to each other to make up the multiple rope unit or system 20 f. In some aspects, the plurality of ropes 20 a, 20 b, 20 c are braided or twisted together to keep the ropes 20 a, 20 b, 20 c from separating and to maximize the overall working load limit and tensile strength of the multiple rope unit.

The ropes 20 a, 20 b, 20 c may each include a plurality of structural strands 22 that may be comprised of any suitable number of yarns and fibers fabricated from any suitable natural or synthetic material, or combination of natural and synthetic materials. The ropes 20 a, 20 b, 20 c may have any working load limit and any tensile strength. The systems and methods are useful, among other things, for mooring, lifting, winching, and hoisting applications, or any other applications in which snap back is a concern.

Any of the ropes 20 a, 20 b, 20 c in the multiple rope unit may be comprised of natural fibers, synthetic fibers, or a combination of any suitable proportion of natural fibers and synthetic fibers. In a given multiple rope unit, different ropes 20 a, 20 b, 20 c made of different fibers may be used such that not all of the ropes 20 a, 20 b, 20 c are natural ropes 20 a, 20 b, 20 c or not all of the ropes 20 a, 20 b, 20 c are synthetic ropes 20 a, 20 b, 20 c. In some aspects, all of the ropes 20 a, 20 b, 20 c are made of the same material.

At least one of the ropes 20 a, 20 b, 20 c, among the plurality of ropes 20 a, 20 b, 20 c in the multiple rope unit of the fifth preferred embodiment includes one or more pre-failure indicator strands 30. Accordingly, certain of the ropes 20 a, 20 b, 20 c preferably do not include the pre-failure indicator strands 30 and are constructed of one or more structural strands 22 without the pre-failure indicator strand 30 therein. The one or more pre-failure indicator strands 30 preferably has the same properties as described above, in terms of make-up, size, location within the rope 20, and ultraviolet, fatigue, abrasion, or dry rot degradation potential. The one or more pre-failure indicator strands 30 preferably has a tensile strength that is less than the tensile strength of the multiple rope unit or the tensile strength of the structural strands 22, such that the one or more pre-failure indicator strands 30 break at a tension that is less than the tension under which the multiple rope unit will fail, including a tension that is less than the tension under which the ropes 20 that make up the multiple rope unit will break. The tensile strength of the one or more pre-failure indicator strands 30 may be at or slightly above the working load limit of the multiple rope unit, which itself is higher than the working load limit of the individual ropes 20 a, 20 b, 20 c that make up the unit, and substantially below the tensile strength of the multiple rope unit, which itself is higher than the tensile strength of the individual ropes 20 a, 20 b, 20 c that make up the unit. The tensile strength of the one or more pre-failure indicator strands 30 preferably lies between the working load limit and the tensile strength of the multiple rope unit or the structural strands 22 such that the one or more pre-failure indicator strands 30 will break before the multiple rope unit fails by having one or more of the ropes 20 a, 20 b, 20 c break. The one or more pre-failure indicator strands 30 serve to convey that the multiple rope unit is stressed such that corrective action or clearance of the snap back zone or other zone in the vicinity of the multiple rope unit may be undertaken well in advance of the failure of the multiple rope unit.

The one or more pre-failure indicator strands 30 are preferably operably connected to an indicator, such as the RFID tags 40, the fiber optic cable 50, the conductive wire 60 or the indicator dye 70, that generates a detectable signal or is otherwise capable of generating a detectable signal. The one or more pre-failure indicator strands 30 may comprise a conduit for this detectable signal such that the detectable signal may traverse the one or more pre-failure indicator strands 30. In some aspects, the one or more pre-failure indicator strands 30 include the plurality of active RFID tags 40 of the first preferred embodiment, as described above for the one or more pre-failure indicator strands 30 used in accordance with the rope 20 c (FIG. 3 and FIG. 4) in the multiple-rope unit. In some aspects, the one or more pre-failure indicator strands 30 include the one or more fiber optic cables 50 of the second preferred embodiment, as described above for the one or more pre-failure indicator strands 30 used in accordance with a single rope 20 b (FIG. 5) in the multiple-rope unit. In some aspects, the one or more pre-failure indicator strands 30 comprise a conductive wire 60 as described above for the one or more pre-failure indicator strands 30 used in accordance with a single rope 20 b (FIG. 6) in the multiple-rope unit. In some aspects, the one or more pre-failure indicator strands 30 comprise the indicator dye 70 as described above for the one or more pre-failure indicator strands 30 used in accordance with a single rope 20 b (FIG. 7) in the multiple-rope unit.

The disclosure also features methods for detecting a pre-failure condition in the rope 20 or in ropes 20 a, 20 b, 20 c in the multiple rope unit. In general, the methods comprise determining whether one or more pre-failure indicator strands 30 of one or more ropes 20, 20 a, 20 b, 20 c have broken by detecting the presence or the absence of a detectable signal generated by an indicator operably connected to the one or more pre-failure indicator strands 30 and, optionally, taking remedial action to avoid failure of the one or more ropes 20, 20 a, 20 b, 20 c and/or emitting an audible alarm, a visible alarm, and/or a tactile alarm if it is determined that one or more pre-failure indicator strands 30 of the one or more ropes 20, 20 a, 20 b, 20 c have broken. The methods may be used in accordance with any rope pre-failure indicator system 10 a, 10 b, 10 c, 10 d, 10 f described or exemplified herein. The rope 20, 20 a, 20 b, 20 c may be a mooring rope 20, 20 a, 20 b, 20 c, which may be under water.

Referring to FIGS. 1-2D, in operation, the rope pre-failure indicator systems 10 a, 10 b, 10 c, 10 d, 10 f are used to determining whether the pre-failure indicator strands 30 of the rope 20 have broken. The systems 10 a, 10 b, 10 c, 10 d, 10 f are able to monitor the ropes 20 by detecting the presence or the absence of the detectable signal generated by an indicator, such as the RFID tags 40, the detectors 58 a, 58 b, 68 a, 68 b or the indicator dye 70. The RFID tags 40, the detectors 58 a, 58 b, 68 a, 68 b or the indicator dye 70 are operably connected to the pre-failure indicator strands 30 such that the signal or indication is provided when the indicator strand 30 fails or is stressed to a degree that prompts the indication. The user, upon receipt of the indication or warning is able to take remedial action to avoid failure of the rope 20. The indication that the indicator strand 30 fails or is stressed preferably comprises an audible alarm, a visible alarm, and/or a tactile alarm. The indicator strands 30 may include a fiber optic cable 50 with a light signal passing therethrough. The fiber optic cable 50 may be comprised of a duplex fiber optic cable 50.

Referring to FIGS. 2B and 2C, in the second and third preferred embodiments, the first and/or second terminals 54 a, 54 b, 64 a, 64 b may include a time-domain reflectometry (“TDR”) device 60 a, 60 b, 70 a, 70 b. The TDR device 60 a, 60 b, 70 a, 70 b is preferably able to send a pulse signal into the fiber optic cable 50 or the conductive wire 60 and the time until a return pulse is sensed by the first and/or second terminals 54 a, 54 b, 64 a, 64 b is recorded. The recorded time is preferably transmitted to the receiver 52, 62, which calculates the length of the cable 50 or wire 60 until there is a discontinuity. The discontinuity may be indicated as an opposite end of the cable 50 or wire 60 or may be an intermediate position along the cable 50 or wire 60. If the discontinuity is the opposite end of the cable 50 or wire 60, the receiver 52, 62 determines that the rope 20 is operating properly or is structurally functional, the receiver 52, 62 indicates a potential failure of the rope 20. In addition, based on the calculation, the receiver 52, 62 may be able to determine where along the length of the rope 20, the discontinuity occurs and preferably communicates this information to the user, operator or technician, such that the rope 20 can be inspected at the indicated portion. The TDR device 60 a, 60 b, 70 a, 70 b may be incorporated into the first and second terminals 54 a, 54 b, 64 a, 64 b, may be incorporated into only one of the first and second terminals 54 a, 54 b, 64 a, 64 b or may be comprised of a separate device that is selectively operable with the rope 20 for inspection purposes.

The rope pre-failure indicator systems 10 b, 10 c of the second and third preferred embodiments are not limited to inclusion or incorporation of the TDR device 60 a, 60 b, 70 a, 70 b and may operate without the TDR device 60 a, 60 b, 70 a, 70 b. The inclusion of the TDR device 60 a, 60 b, 70 a, 70 b is preferred as the TDR device 60 a, 60 b, 70 a, 70 b provides the ability to determine a location of a discontinuity and to determine where damage may have occurred to the rope 20 along its length. Such location of damage can be advantageous in relatively long ropes 20, ropes 20 where access to portions of the rope 20 is difficult or ropes 20 where gaining access to one of the ends of the ropes 20 is difficult. The TDR device 60 a, 60 b, 70 a, 70 b is also advantageous in that only one end of the rope 20 is required for access as the TDR device 60 a, 60 b, 70 a, 70 b sends a signal from the same end of the rope 20 that the return signal is received. Accordingly, the TDR device 60 a, 60 b, 70 a, 70 b may be selectively applied to one end of the rope 20, such as a rope 20 used to support a floating structure in a body of water where one end of the rope 20 is submerged in fluid and is generally not accessible. In these situations, the TDR device 60 a, 60 b, 70 a, 70 b can be transported for interaction with the end of the rope 20 extending out of the fluid for sending the signal, receiving the return signal and transmission of the results for calculation. Such portable TDR devices 60 a, 60 b, 70 a, 70 b can be used to conduct periodic tests on the rope 20 for sample testing or for testing during service downtime of the rope 20 or the structure associated with the rope 20. The TDR device 60 a, 60 b, 70 a, 70 b is not limited to being portable or to being operated from only one end of the rope 20 and the TDR device 60 a, 60 b, 70 a, 70 b may be integrated with the first and second terminals 54 a, 54 b, 64 a, 64 b or may be otherwise arranged for inspection of the rope 20. Integration of the TDR device 60 a, 60 b, 70 a, 70 b with the first and second terminals 54 a, 54 b, 64 a, 64 b may be advantageous for applications where constant checking or testing of the rope 20 is desired, such as static applications or for ropes 20 having a relatively consistent load during a relatively long service time.

The TDR device 60 a, 60 b, 70 a, 70 b is preferably able to sound an alarm or provide a warning to the user, operator or other predetermined personnel when the return signal indicates a discontinuity in the fiber optic cable 50 or the conductive wire 60 at a location other than the opposite end of the fiber optic cable 50 or the conductive wire 60. Such warnings or notifications are particularly useful in applications such as winching, where the rope 20 could be attached to a drum end or in static applications, such as a structure where a permanent connection would be made. The warning would provide an indication to the user, operator or other predetermined personnel that the rope 20 requires further inspection, removal, replacement, repair or other remediation.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

We claim:
 1. A pre-failure indicator system for determining a degradation or failure condition, the pre-failure indicator system comprising: a rope having an elongated structural strand and a pre-failure indicator strand, the pre-failure indicator strand comprised of a conductive wire and configured to fail when the rope is subject to tension that is less than the tensile strength of the structural strand; an indicator that generates a detectable signal when the pre-failure indicator strand fails; and a transceiver that detects the detectable signal, the transceiver configured to transmit a warning upon receipt of the detectable signal.
 2. The pre-failure indicator system of claim 1, wherein the structural strand is comprised of a plurality of structural strands.
 3. The pre-failure indicator system of claim 1, wherein the conductive wire is comprised of a multiple conductive wires.
 4. The pre-failure indicator system of claim 1, wherein the conductive wire is constructed of a metal.
 5. The pre-failure indicator system of claim 4, wherein the metal is comprised of one of copper and silver.
 6. The pre-failure indicator system of claim 1, wherein the indicator includes an electrical signal generator and the detectable signal comprises an electrical signal.
 7. The pre-failure indicator system of claim 1, wherein the conductive wire is constructed one of carbon fibers and a conductive polymeric material.
 8. The pre-failure indicator system of claim 1, wherein the conductive wire includes a first end and a second end, a first terminal connected to the first end and a second terminal connected to the second end.
 9. The pre-failure indicator system of claim 8, wherein the first terminal includes a first electronic signal transmitter, a first electronic signal receiver and a first electronic signal transceiver.
 10. The pre-failure indicator system of claim 1, wherein the conductive wire is constructed of a material designed and configured to degrade at a faster rate than the structural strand based on exposure an environmental factor, the environmental factor selected from the group consisting of ultraviolet radiation, abrasion and dry rot.
 11. The pre-failure indicator system of claim 1, further comprising: a time-domain reflectometry (“TDR”) device associated with a first terminal of the rope, the TDR device configured to send a pulse signal into the pre-failure indicator strand and sense a time until a return pulse is received at the TDR device, the time being recorded.
 12. A pre-failure indicator system for determining a degradation or failure condition, the pre-failure indicator system comprising: a multiple rope unit including a plurality of ropes, a first rope of the plurality of ropes including a pre-failure indicator strand having a tensile strength less than a tensile strength of the multiple rope unit such that the pre-failure indicator strand fails when the multiple rope unit is subject to tension that exceeds the tensile strength of the pre-failure indicator strand before the multiple rope unit fails, the pre-failure indicator strand comprised of a conductive wire; an indicator that generates a detectable signal associated with the pre-failure indicator strand; and a transceiver that detects the detectable signal and transmits a warning upon receipt of the detectable signal.
 13. The pre-failure indicator system of claim 12, wherein the plurality of ropes also includes a second rope and a third rope.
 14. The pre-failure indicator system of claim 12, wherein each of the plurality of ropes is constructed of a material selected from the group consisting of synthetic fibers, natural fibers and a combination of synthetic and natural fibers, each of the plurality of ropes including a plurality of structural strands.
 15. The pre-failure indicator system of claim 12, wherein the conductive wire is constructed of a metallic material.
 16. A pre-failure indicator system for determining a degradation or failure condition, the pre-failure indicator system comprising: a rope including a plurality of structural strands and a pre-failure indicator strand, the pre-failure indicator strand having a tensile strength less than a tensile strength of the structural strands such that the pre-failure indicator strand fails when the rope is subject to tension that exceeds the tensile strength of the pre-failure indicator strand, the pre-failure indicator strand comprised of a conductive wire having a first end and a second end; a first signal source connected to the first end and configured to impart a signal into the conductive wire; a signal detector connected to the conductive wire and configured to detect the signal and convert the signal; and a signal transmitter in communication with the signal detector, the signal transmitter configured to transmit the converted signal.
 17. The pre-failure indicator system of claim 16, wherein the structural strands are constructed from a material selected from the group consisting of natural fibers, synthetic fibers and a combination of natural and synthetic fibers.
 18. The pre-failure indicator system of claim 16, wherein the conductive wire is constructed of a metallic material.
 19. The pre-failure indicator system of claim 16, wherein the signal is comprised of an electric current.
 20. The pre-failure indicator system of claim 16, wherein the signal source is selected from the group consisting of signal generator, an analog signal generator, a function generator, a microwave signal generator, a pitch generator, an arbitrary waveform generator and a frequency generator. 